Harness for carrying a load

ABSTRACT

A harness for a back-pack comprises a chest harness A, a strut mechanism in the form of a flexible spine B and a hip belt C. The flexible spine B provides a sprung, damped connection between the chest harness A and the hip belt C, so that the load of the backpack is transferred through the flexible spine B to the hip belt C, while the flexible spine can extend to accommodate movement of the wearer&#39;s body. The chest harness A comprises straps  12, 15  which are interconnected at the front of the wearer by a buckle  14 . Abdominal straps  15  are connected to the buckle  14  by flexible wands  16  which flex under the breathing action of the wearer to retain the load securely against the wearer&#39;s back without restricting breathing.

FIELD OF THE INVENTION

This invention relates to a harness for carrying a load, and isparticularly, although not exclusively, concerned with a harness for usewith a backpack such as a rucksack.

BACKGROUND OF THE INVENTION AND PRIOR ART

Conventional rucksacks comprise a pack provided with a waistband whichextends around the wearer's waist above the hips, and a pair of shoulderstraps which extend from positions near or at the base of the pack overthe front of the wearer and over the shoulders to be attached to thepack adjacent the back of the wearer on each side of the pack. Theintention is for the load carried in the pack to be supported primarilyby the waistband rather than the shoulders, and to minimise any tendencyof the load to pull backwards on the wearer.

Such conventional rucksacks have the following disadvantages:

1. The shoulder straps are connected by the pack (and sometimesdirectly) to the waistband. Consequently, the rucksack is not able toconform fully to movements of the wearer. In particular, typicalmovements of the wearer involve significant variation in the distancebetween the top of the shoulders and hips, for example during movementsof the shoulders or sideways bending of the torso. Also, this distancecan vary as a result of the extension of the spine during bending andtwisting. Tests have shown that the spine extends by approximately 6 cmwhen a person moves from an upright position to touch their toes. Strapsin conventional rucksacks have a vertically load-bearing function, andare connected to the base of the pack at each side. Consequently, therecan be little vertical movement between the shoulder straps and thewaistband, with the result that any variation in the distance betweenthe wearer's shoulders and their hips means that the weight distributionof the pack constantly shifts between the waistband and the shoulderstraps. The result of this is that the pack tends to bounce on theshoulders, with the waistband riding upwards on the hips. This isparticularly prevalent when the wearer is performing faster movementssuch as running. The usual response of the wearer is to tighten theshoulder straps to restrict bouncing, but this results in more of theweight of the pack being supported by the shoulders. As a consequence,the wearer tends to round their shoulders and stoop forwards, soeliminating the natural curvature of the spine and causing excessivestrain on both the spine and the muscles of the pack. This additionalstrain is exacerbated by any remaining “bounce” which occurs.

2. In conventional rucksacks, the shoulder straps are intended to carryapproximately 30% of the load, with the remainder being supported by thewaistband. The shoulder straps pass over the top of the acromion (theextension of the shoulder blade that connects to the end of the claviclebone), which is attached to the main skeletal structure through musclesand other soft tissues. As a result the wearer experiences significantmuscle fatigue when wearing the pack for any length of time. Since theacromion is highly mobile with any shoulder movement, movement of thearms exacerbates this muscle fatigue in the shoulder and back.Additionally the slope of the top of the shoulders and the weight of therucksack pulling on the shoulder straps pulls the straps backwards andsideways away from the centre of the body.

In order to overcome this effect, it is known to provide chest strapswhich extend between the shoulder straps at the front of the wearer'sbody. The purpose of these chest straps is to prevent the shoulderstraps from slipping sideways off the shoulders. The chest straps do notsupport any vertical load, typically being elasticated, and so are noteffective to transfer loads from the pack to the wearer's body.

3. Conventional rucksacks draw the entire back panel of the rucksack(i.e. the panel facing the wearer) against the wearer's back by way ofthe waist belt and shoulder straps. Consequently, the rucksack cannotaccommodate relative movement between different parts of the wearer'sback. Also, the pack is pressed against moving parts of the body, and inparticular the highly mobile shoulder blades. This restricts thewearer's movements, and causes discomfort from rubbing of the wearer'sbody against the pack.

To alleviate these problems, it is known to use a tensioned mesh backpanel that creates an airspace between the pack and the wearer's back tokeep it cool and free of perspiration. However, this reduces the loadsupport, and pushes the pack load further behind the wearer so tendingto pull the wearer backwards. A similar problem arises if extra paddingis applied, especially over the shoulder blades. While this mayalleviate some discomfort, it does not address the root cause of theissue and can additionally restrict the wearer's movements.

The issues referred to above become particularly acute as the wearer'smovements become faster and/or more extreme, for example when the weareris running. Consequently, backpacks intended for runners tend to berelatively lightweight, without a load-bearing waistband or any othermechanism for transferring load onto the wearer's hips. The load is thussupported fully by the shoulders, so severely restricting the load thatcan realistically be carried.

4. As mentioned above, a conventional response to a rucksack “bouncing”on the wearer's back is to tighten the shoulder straps and conventionalshoulder straps do not secure a pack to the wearer's upper back asclosely as users typically would like. However, conventional designscannot overcome this as any conventional solutions cannot preventrestriction of the wearer's breathing, since the breathing action isaccompanied by expansion and contraction of the rib cage.

SUMMARY OF THE INVENTION

According to one aspect of the present invention there is provided aharness for carrying a load, the harness comprising a support structureprovided with a strap arrangement for retaining the support structureadjacent a wearer's back, the strap arrangement comprising left andright chest straps, each chest strap comprising a loop extending from afirst position on the support structure on one side of the supportstructure to a second position below the first position on the same sideof the support structure, the chest straps being interconnected, in use,at the front of the wearer by a releasable buckle comprising left andright buckle components, each loop comprising an upper flexible portionextending from the support structure to an upper fastening point on therespective buckle component and a lower flexible portion extending fromthe support structure to an attachment point at one end of a link, theother end of the link being connected to a lower fastening point on therespective buckle component, whereby the attachment points of the lowerflexible portions are laterally displaceable towards and away from eachother by deflection of at least one of the links (16).

This arrangement enables the harness to be fitted tightly to thewearer's back by means of the chest straps, while permitting thewearer's rib cage to expand when breathing in, such expansion beingaccommodated by movement apart from each other of the attachment pointsof the lower flexible portions.

The loop of each chest strap may be made from a substantiallyinextensible material so that rib cage expansion is accommodatedsubstantially solely by lateral displacement of the attachment points ofthe lower flexible portions. The length of each loop may be adjustableso that the harness can be adapted to the body shape and size of thewearer.

The buckle components, when engaged with each other, may form a rigidinterconnection between the loops. As a result, vertical forces can betransmitted between the loops.

Each link may comprise an inextensible but flexible wand. Each wand maybe rigidly connected to the respective buckle component, so thatdeflection of the links is achieved by flexure of the respective wand.In an alternative embodiment, each wand may be substantially rigid, butconnected to the respective buckle component in a resiliently pivotingmanner.

The harness may comprise a hip belt connected to the support structureby a strut mechanism which, in use, resiliently biases the supportstructure upwards with respect to the hip belt.

The strut mechanism may comprise the sole force transmitting connectionbetween the hip belt and the support structure. The strut mechanism maybe laterally flexible.

According to another aspect of the present invention, there is provideda harness for a backpack comprising a support structure provided with astrap arrangement for retaining the support structure adjacent awearer's back, the harness also comprising a hip belt connected to thesupport structure by a strut mechanism which, in use, resiliently biasesthe support structure upwards with respect to the hip belt, the strutmechanism comprising at least one telescopic strut.

In the context of this specification, a telescopic strut is to beunderstood as a strut comprising two components which are linearlyslidable one within the other to vary the length of the strut.

In one embodiment, a spring may be provided which acts in a direction toextend the strut mechanism, and means may be provided for dampingextension of the strut mechanism.

The strut mechanism may comprise a single upwardly extending strutdisposed substantially centrally of a wearer's back when in use. Thestrut mechanism may comprise a telescopic strut having a pistondisplaceable in a cylinder, the piston and the cylinder being connectedrespectively to one and the other of the hip belt and the supportstructure.

The strut mechanism may incorporate a piezoelectric device to generateelectricity.

The present invention also provides a backpack comprising a harness asdefined above.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the present invention and to show moreclearly how it may be carried into effect, reference will now be made,by way of example, to the accompanying drawings, in which:

FIG. 1 shows a rucksack;

FIG. 2 shows the rucksack of FIG. 1 positioned on a wearer;

FIG. 3 is a sectional view of a sprung, damped strut mechanism suitablefor use with the rucksack of FIGS. 1 and 2;

FIGS. 4a and 4b show a strap arrangement of the rucksack of FIGS. 1 and2 in different configurations;

FIG. 5 shows a support frame of an alternative embodiment of a rucksack;and

FIG. 6 shows a harness positioned on a wearer and supporting a gascylinder.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In this specification, the terms left, right, up, down, front and backand similar directional or positional terms refer to the harness whenworn by a wearer standing upright and as perceived by the wearerthemselves.

As shown in FIG. 1, the rucksack comprises a harness H on which a pack Pis mounted. The harness comprises a support structure comprising acentral spar 9 and a pair of lateral spars 10 to which are connected achest strap arrangement A, a strut mechanism B and a hip belt C.

The chest strap arrangement A comprises left and right chest straps,each of which forms with the support structure a closed loop and is madeup of an upper flexible portion 12 and a lower flexible portion 15, madefrom flexible webbing. Each flexible portion 12 is connected at itsupper end to an upper part of the respective lateral spar 10 and eachlower flexible portion 15 is connected at its lower end to the samelateral spar 10 as the upper flexible portion 12 of the same cheststrap, at a position approximately midway between the upper and lowerends of the respective lateral spar 10.

The upper and lower flexible portions 12, 15 of each chest strap areinterconnected at their ends opposite the attachment points to thesupport structure 9, 10 by a respective buckle component 14 and a linkin the form of a flexible wand 16. Thus, the end of each upper flexibleportion 12 away from its attachment point to the support structure 9, 10is attached to an upper region of the respective buckle component 14 atan upper fastening point on the buckle component 14. The upper end ofthe flexible wand 16 is rigidly secured to the lower region of thatbuckle component 14 at a lower fastening point on the buckle component14, while the lower end of the flexible wand 16 is attached at anattachment point to the end of the lower flexible portion 15 away fromits attachment point to the support structure 9, 10. The flexible wands16 may, for example, be made from a stiff composite material which isresiliently flexible in bending under the forces applied to it duringbreathing of a wearer of the rucksack as will be described below.

The buckle components 14 of the two chest straps 12, 15, can beinterconnected in a rigid manner, i.e. a manner which does not permitrelative vertical displacement between them. Consequently, when thebuckle is fastened, the chest straps 12, 15 can transfer vertical forcesbetween them through the buckle 14.

The upper and lower flexible portions 12, 15 are provided withadjustment buckles which enable the chest straps to be adjusted to fitthe individual size and shape of the wearer.

The hip belt C is made from flexible webbing provided with a waistbuckle mechanism incorporating adjustment means to enable the waist beltto be fitted to the wearer. The hip belt C is connected to the supportstructure 9, 10 only by the strut mechanism B but is otherwise movablewith respect to the support structure 9, 10.

The strut mechanism B shown in FIGS. 1 to 3 comprises a piston 4 whichis movable within a cylinder 8. A spring 5 acts between the lower end ofthe cylinder 8 and a flange 3 on the flexible rod 2. The piston 4,cylinder 8 and spring 5 are accommodated within a housing 18 which ismounted on the inside face of the back panel 13 of the pack P in orderto protect the strut mechanism from the contents of the pack P. Thehousing 18, the cylinder 8, the back panel 13 and the central spar 9 ofthe support structure are secured together, for example by means of ascrew and nut fastener 30. There is a hole 17 in the back panel 13 belowthe end of the central spar 9 through which the flexible rod 2 extends,to be connected to the hip belt C as shown in FIGS. 1 and 2. Theflexible rod 2 is adjustable with respect to the hip belt C by means ofa screw adjuster 11.

For use the rucksack is placed on a wearer as shown in FIG. 2. With thebuckle 14 undone, and the buckle on the hip belt C undone, the wearerpasses his or her arms through the loops formed by the flexible portions12, 15, 14 and 16. The buckle 14 is then fastened at the wearer's chest,and the hip belt buckle is fastened at the front of the wearer'sabdomen. The upper and lower flexible portions 12 and 15 are adjusted bymeans of their adjustment buckles to provide a tight fit for the cheststrap arrangement A while allowing easy breathing of the wearer as willbe discussed below. The hip belt is similarly tightened to provide acomfortable yet secure fit around the wearer's abdomen so that the hipbelt C rests on the wearer's hips.

When the wearer is stationary and standing upright as shown in FIG. 2,the load in the pack P is secured to the wearer's upper torso by thechest strap arrangement A and so is prevented from falling backwardsaway from the wearer's torso. However, the weight of the load in thepack P is transferred by the strut mechanism B substantially entirely tothe hip belt C and is then spread sideways from the single pointconnection 1 onto the hips of the wearer. The single point connection 1is situated centrally at the back of the hip belt C and at the top ofthe hip belt C so as to maximise the use of the concave curvature of thewearer's lumbar region (i.e. the small of the back) to bring the pointof application of the load at the single point connection 1 as farforward into the wearer's back as possible. The rod 2 serves as the solecomponent transferring the load from the pack P to the hip belt C. Thespring 5 in the strut mechanism B resists compression but allowsextension by sliding of the rod 2 in the cylinder 8. Also, theflexibility of the rod 2 allows relative movement between the supportstructure 9, 10 and the hip belt C in lateral, forwards and backwardsdirections.

The resistance to compression of the strut mechanism B ensures that theweight of the load in the pack P is fully transferred into the hip beltC to be supported by the wearer's hips. The strut mechanism B extendsfrom the top of the hip belt C at the lowest part of the lumbar regionup the full length of the lumbar region to meet the support structure 9,10 in the thoracic region of the wearer's torso. As a result, the strutmechanism covers the full length of the lumbar region where the mostflexion and extension of the wearer's spine will occur during typicalmovement. The flexibility and free extension of the strut mechanism Benables the chest strap arrangement A, and the load in the pack P, tomove in all directions independently of the hip belt C so as to avoidany restriction of the wearer's movements.

The spring 5 supports the weight of the load throughout the range ofextension of the strut mechanism B. The spring 5 may be replaced by aseries of springs, which may have different spring rates so that in thefully extended position the spring rate of the strut mechanism B as awhole is low, but increases as the springs are compressed. This enablesthe spring rate to adjust automatically for different weights of load inthe pack P.

Movement of the load is damped by controlling the movement of the piston4 within the cylinder 8. The head of the piston 4 is flanged as shown sothat in the compression stroke, as the weight of the load pushes down onthe cylinder so that the piston 4 moves towards the top end of thecylinder 8, air can easily escape past the piston head. However, in theextension stroke, as the recoil force of the spring or springs fivebrushes upwards on the cylinder 8 so that the piston 4 moves towards thebottom of the cylinder 8, the air pressure above the piston 4 decreases.The greater air pressure below the piston 4 forces the flange of thepiston head against the sides of the cylinder, thereby restricting themovement of their past the piston 4. The resulting air pressuredifferential resists the movement of the piston 4 relative to thecylinder 8 and thereby provides a velocity-dependent damping force onthe movement of the load under the action of the springs 5 during theextension phase of the cycle. A hole 6 near the top of the cylinder 8allows air to flow between the ambient surroundings and the interior ofthe cylinder 8 in either direction. The damping effect may be varied bychanging the flow passage of the hole 6 by means of an adjusting screw 7fitted within the hole 6. This enables the damping effect to be adjustedfrom a relatively soft rating with a low damping effect to maximisecomfort for slow activities such as walking, and a hard rating with ahigh damping effect for faster or more vigorous activities such asrunning where extreme movements would otherwise destabilise the wearer.

The damping mechanism provided by the piston 4 and the cylinder 8 isthus a one-way mechanism which damps movement on the extension cyclewhen the springs 5 are in recoil but not on the compression cycle whenthe weight of the load is compressing the springs. It will beappreciated that the damping system shown in FIG. 3 is only one possiblemechanism which can provide the desired effect. Other dampingmechanisms, example a simple friction damper, a gas strut or a hydrauliclinear decelerator could be used to produce the same result.

To achieve a comfortable fit, the optimal distance between the hip beltC and the chest strap arrangement A, with the wearer in a static,upright position, will vary from individual to individual. Also, therequired static length of the strut mechanism B will vary depending onthe load carried in the pack P, since a heavy load will compress thesprings 5 more than a light load. For these reasons, and adjustmentmechanism to vary the static length of the strut mechanism B isdesirable. Suitable mechanisms will be apparent to the skilled person,such as a screw threaded adjustment mechanism as shown in FIG. 1, inwhich the cylindrical sleeve 11 can be rotated on a screw threadedcolumn 32 attached to the hip belt C to adjust the overall length of thestrut mechanism B to suit the individual wearer and/or the load to becarried.

When the wearer is standing still and upright, the weight of the load inthe pack P is transmitted from the lateral spars 10 to the central spar9 and thence to the cylinder 8 to compress the springs 5 until a staticequilibrium position is reached. Provided that the strut mechanism B isadjusted to a sufficient length, the rigidity of the support structure9, 10 ensures that the weight of the load is transferred directly intothe strut mechanism B so that it is supported by the hip belt C, and thechest strap arrangement 12, 15 does not provide any vertical support forthe load. From this steady-state condition, forwards bending of thewearer will lift some of the weight of the load from the strut mechanismB and this will be taken by the wearer is inclined back. This movementis accompanied by extension of the springs 5 so that the strut mechanismincreases in length to match the increased distance between the cheststrap arrangement a and the hip belt C. Static equilibrium is thusrestored in this new position, with the load supported in part by thehip belt C and in part by the wearer's inclined back, but the cheststrap arrangement 12, 15 still does not support any substantial portionof the load. The effect of this is that no weight is carried by theshoulders, nor are there any forces pulling the hip belt C off itssecure position on the wearer's hips. The piston-cylinder unit 4, 8 andthe springs 5 need to accommodate an extension of around 6 cm in thespine of an average wearer from fully loaded to fully extended as thewearer moves from an upright position to a “touching toes” position.During typical walking motions the load will move up and down and thekinetic energy will be absorbed and returned by the springs 5 reducingthe impact on the wearer's hips. The damping effect will be slight atthese low speeds. During faster movement such as running, the kineticenergy produced by the moving load is greater. The springs respond toabsorb and return this great energy and, in an undamped system, wouldexacerbate the amplitude of the load's cycle. However, the dampingachieved by the configuration of the head of piston 4, which has moreeffect at great speeds, controls the movement of the load and the cycleamplitude to keep them within the tolerances of the wearer's naturalgait; this is perceived by the wearer as reducing the “bounce” of therucksack when running.

The chest strap arrangement A is in the general form of an X-harness. Itserves to secure the vertical central spar 9 over the wearer's spinebetween the shoulder blades. From this vertical spar 9 the supportstructure 9, 10 extends left and right across the top of the back abovethe shoulder blades to the top corners of the pack P, which sit higherthan the wearer's shoulders. The lateral spars 10 then descend from thetop corners of the pack P down the sides of the pack. The upper flexibleportions 12 of the chest strap arrangement A, which can be regarded asshoulder straps, extend from the support structure 9, 10 over the frontof the clavicle blown on each side of the wearer's neck and down acrossthe wearer's chest at a high enough position to avoid the pectoralmuscles, to the buckle 14 disposed over the wearer's sternum. The lowerflexible portions 15 of the chest strap arrangement A, which can beregarded as abdomen straps, are connected to the lateral spars 10 of thesupport structure at approximately the level at which these lateralspars 10 are connected to the central spar 9, which coincides generallywith the lower part of the thoracic region of the wearer. The abdomenstraps 15 extend from this position around the rib cage to the lowerends of the flexible wands 16. The shoulder straps 12 and the abdomenstraps 15 are all adjustable to provide a comfortable fit on the wearer

The buckle 14 comprises a left component connected to the left shoulderstrap 12 and the left abdomen strap 15, so that when the buckle isunfastened as in I FIG. 1, the left shoulder strap 12, the leftcomponent of the buckle 14, the left abdomen strap 15, the flexible wand16 and the vertical spar 9 running down the wearer's spine together forma single continuous loop. The corresponding components on the right ofthe wearer form a similar single continuous loop. The left and rightcomponents of the buckle 14, when interconnected, form a rigid unit sothat the two components are fixed in position with respect to eachother. The interconnected buckle has a relatively narrow profile so asto avoid interfering with the pectoral muscles or breasts of the wearer.

Each flexible wand 16 is rigidly secured to the respective component ofthe buckle 14 and extends downwardly for several centimetres (forexample at least 8 cm or 10 cm) below the sternum. The flexible wands 16are substantially inextensible in the lengthwise direction so as toresist linear forces, but are flexible laterally. The left abdomen strap15 is connected to the bottom of the flexible wand 16 on the left bucklecomponent and the right abdomen strap 15 is connected to the bottom offlexible wand 16 on the right buckle component

The shoulder straps 12 are connected to the top of the respective bucklecomponent at an angle so that, when the buckle 14 is connected in usethe forces are directed diagonally across the wearer's torso from theleft shoulder strap 12 through the buckle 14 and the wand 16 to theright abdomen strap 15 and from the right shoulder strap 12 the forcesare directed through the buckle 14 and the wand 16 to the left abdomenstrap 15. Since the shoulder straps 12, the abdomen straps 15, thebuckle components 14 and the flexible wands 16 are substantiallyinextensible, the components form two close-fitting loops runningdiagonally around the wearer's body to secure the chest straparrangement to the wearer's torso.

Because the wands 16 are laterally flexible, the gap between the bottomends of the wands 16 can increase and decrease with the expansion andcontraction of the wearer's rib cage during breathing. This is shown inFIGS. 4a and 4b . FIG. 4a shows the wands 16 extending generallyvertically downwards from the buckle 14 when the wearer has fullyexhaled, while FIG. 4b shows the wands 16 pulled apart sideways by theabdomen straps 15 when the wearer has inhaled and the rib cage is fullyexpanded. The variation in the horizontal distance around the lower partof the wearer's rib cage during breathing is accommodated in this mannerwhile maintaining a substantially constant length for the diagonal loopcomprising the left shoulder strap 12, the buckle component 14, the wand16 and the right abdomen strap 15 and vice versa. The chest straparrangement A thus remains securely fastened to the wearer's torso,ensuring that the pack P remains held tightly against the wearer's back.

The structure of the buckle 14 and the flexible wands 16 thus allow thewearer to breathe freely while fitting securely around the wearer'storso at positions which move little as the posture of the wearerchanges during normal body movements such as walking and running or whenbending forwards, backwards or sideways. This minimises the shifting ofthe straps 12, 15, rubbing against the wearer's body, or slack in thechest strap arrangement A. Also, the load is securely and comfortablyfixed to the wearer's back, with the chest strap arrangement A sittingon the wearer's skeletal structure while avoiding large muscle groups soreducing muscle fatigue and strain and facilitating heat loss.

The back panel 13 of the pack P is relatively stiff to ensure that thecontents of the pack do not bulge between the spars 9, 10 of the supportstructure to interfere with the wearer's body. Padding is provided overthe entire central spar 9 and the area of the support structure 9, 10extending across the top of the back above the shoulder blades. Thispadding serves to cushion the impact of the harness on immovable partsof the wearer's torso and also serves to hold the back panel 13 awayfrom the wearer's body to ensure that the shoulder blades are free tomove unconstrained. This also facilitates heat loss out of the side ofthe pack, which may be further improved by means of channels in thepadding. The flexible guiding rod 2 of the strut mechanism B liesbetween the wearer's back and the pack P passing through the hole 17 inthe back panel 13 and down to the hip belt C. The pack P is heldslightly away from the wearer's back by the shaping of the supportstructure 9, 10 and the stiffness of the back panel 13 to ensure theflexible guiding rod 2 is free to move without interference with thewearer's back.

Any movement of the wearer while wearing the harness will createmechanical stress on the strut mechanism B. The damping provided by thecooperation between the piston 4 and the cylinder 8 serves as a shockabsorber to damp the stresses and manage load fluctuations on thewearer's body by dissipating the kinetic energy generated. As anoptional variant, a piezoelectric device or other electrical generatormay be incorporated into the strut mechanism B to convert the kineticenergy generated by movement of the load into electrical energy tocharge and electrical device, example a device constituting part of, oraccommodated within, the pack P.

Although the embodiment of FIGS. 1 to 4 shows a single point attachment1 between the support structure 9, 10 and the hip belt C, the strutmechanism may comprise multiple connections. For example, as shown inFIG. 5, the strut mechanism B may comprise a pair of gas struts 19 whichare connected to the hip belt C at the hips themselves by means ofhinged connections 20 which enable the gas struts to pivot forwards andbackwards relatively to the hip belt C. The gas struts 19 extendupwardly from the hip belt to the lateral wings 34 of the central spar9. While the gas struts 19 of the embodiment of FIG. 5 provide the samegeneral function as that of the strut mechanism B of FIGS. 1 to 4, theydo not require the lateral flexibility of the flexible rod 2. Instead,lateral flexibility of the mechanism is achieved by a difference inextension between the two gas struts 19, while forward, backward andtorsional flexibility is achieved by the hinged connections 20 at thehip belt C combined, when necessary, with differential extension of thestruts 19. The arrangement of FIG. 5 requires an increased extensioncapability compared with that of FIGS. 1 to 4, but the struts 19themselves can be substantially rigid. Both of the gas struts 19 requirelength adjusters 11 to accommodate different loads and lengths ofwearer's backs, so that a comfortable fit for the wearer can be achievedand the strut mechanism B is long enough for the entire weight of theload in the pack P to be transferred into the hip belt C relieving theshoulder straps 12 from the weight of the load.

The use of the gas struts 19 inherently provides a sprung, damped systemin the strut mechanism B, but an alternative possibility is to replacethe gas struts with rigid rods incorporating sprung, damped systems suchas shown in FIG. 3 positioned at the junction between the rigid rods andthe wings 34 of the central spar 9.

FIG. 5 shows the harness without any load such as the pack P of FIGS. 1and 2. In the absence of a pack requiring a relatively rigid supportingframe, the shoulder straps 12 extend from the central spar 9 at positionclose to the centre of the back of the wearer and run, as flexiblecomponents, laterally outwards from the wearer's spine, over theshoulder, and down towards the respective buckle component 14. The loadcan be attached to the central spar 9 at attachment points 21 so thatthe rigidity of the central spar 9 ensures that the weight of the loadis transferred to the gas struts 19 an offence to the hip belt C.

FIG. 6 shows an embodiment in which a load in the form of a gas cylinder23 is secured directly to the hip belt C and is connected to the supportstructure 9 by a free-running connection which is shown, by way ofexample, as a rail 24 on the central spar 9 of the support structure anda runner 25 secured to the upper part of the cylinder 23.

The load (i.e. the gas cylinder 23) may be secured to the hip belt usingelastic connections 22 to create a sprung loading system. The runner 25is connected to the load 23 in a pivotable manner so that it canaccommodate sideways twisting of the chest strap arrangement a relativeto the hip belt C. As with the previous embodiments, complete separationof the chest strap arrangement A and the hip belt C is achieved so thatthe full weight of the load is carried by the hip belt C. the elasticconnection 22, if provided, between the load and the hip belt C may bemade of a material with memory properties to create a complete sprung,damped system, alternatively a damping system such as a friction dampercould be incorporated into the mechanism comprising the rail 24 and therunner 25.

In the embodiment of FIG. 6, the shoulder straps 12, abdomen straps 15,buckle 14 and flexible wands 16 are constructed in the same manner asthose of the previous embodiments.

The embodiments of the present invention that have been described aboveenable the chest strap arrangement A and the hip belt C to moveindependently of each other while retaining the support of the load onthe hips by way of the hip belt C. As shown, for example, in FIG. 1, theconnection between the strut mechanism B and the chest strap arrangementA is at the bottom of the central spar 9. Since most of the extension ofthe wearer's spine during normal body movements occurs in the lumbarregion, this arrangement is adequate in most circumstances. However,some extension and flexion occurs in the thoracic region, andconsequently a more ergonomic fit may be provided by connecting theflexible rod 2 to the support structure 9, 10 at a higher position thanis shown in FIG. 1.

It will be appreciated that, as is conventional, the shoulder straps 12and abdomen straps 15, as well as the hip belt C may be made of flexiblewebbing material or other suitable material known for use in rucksacksand similar load carrying devices. Padding may be provided to increasethe comfort of the wearer, both on the flexible straps and on thesupport structure 9, 10 and any other components of the harness and thepack which contact parts of the wearer's body.

I claim:
 1. A harness for a backpack comprising; a support structureprovided with a strap arrangement for retaining the support structureadjacent a wearer's back, a hip belt; and a strut which connects the hipbelt to the support structure, the strut being disposed substantiallycentrally of a wearer's back and extending between the hip belt and thesupport structure over the full length of the lumbar region of thewearer when in use, the strut being the sole force-transmittingconnection between the hip belt and the support structure, the strutcomprising: first and second components which are linearly slidable onewithin the other to vary the length of the strut, the first and secondcomponents being connected respectively to the hip belt and the supportstructure thereby to permit displacement of the support structuretowards and away from the hip belt by sliding of the first componentwithin the second component, and a load transfer element which actsbetween the first and second components to resist compression of thestrut but to allow extension of the strut.
 2. A harness as claimed inclaim 1, wherein the second component is a cylinder and the firstcomponent is a piston which is slidable within the cylinder.
 3. Aharness as claimed in claim 2, wherein the load transfer elementcomprises a spring which acts in a direction to bias the supportstructure upwards with respect to the hip belt.
 4. A harness as claimedin claim 2, wherein the piston is connected to the hip belt by alaterally flexible piston rod which connects the piston to therespective hip belt or support structure to permit lateral and forwardsand backwards movement of the support structure with respect to the hipbelt,
 5. A harness as claimed in claim 1, wherein the strut includesdamping means for damping movement of the first and second components inthe extension direction.
 6. A harness as claimed in claim 1, wherein thestrap arrangement comprises left and right chest straps.
 7. A harness asclaimed in claim 6, wherein each chest strap comprises a loop extendingfrom a first position on the support structure on one side of thesupport structure to a second position below the first position on thesame side of the support structure.
 8. A harness as claimed in claim 7,wherein the loop of each chest strap is made from an inextensiblematerial.
 9. A harness as claimed in claim 7, wherein the chest strapsare interconnected at the front of a wearer by a releasable bucklecomprising left and right buckle components which, when engaged witheach other, form a rigid interconnection between the loops.
 10. Aharness as claimed in claim 9, wherein the releasable buckle comprises aleft buckle component and a right buckle component, each of the bucklecomponents having a respective upper fastening point and a respectivelower fastening point, the harness further comprising a pair of links,each link being in the form of an inextensible wand which is resilientlyflexible in bending, and comprising a first end and a second end, thefirst end of each wand being connected respectively to the lowerfastening points of the left and right buckle components, wherein thebuckle components, when engaged with each other, form a rigidinterconnection between the loops, and wherein each of the loopscomprises: an upper flexible portion extending from the supportstructure to the upper fastening point on the respective bucklecomponent, and a lower flexible portion extending from the supportstructure to an attachment point at the second end of the respectivewand, whereby the attachment points of the lower flexible portions arelaterally displaceable towards and away from each other by resilientdeflection of at least one of the wands.
 11. A harness as claimed inclaim 10, wherein each wand is rigid and is connected to the respectivebuckle component in a resiliently pivoting manner.
 12. A harness asclaimed in claim 10, wherein each wand is flexible and is rigidlyconnected to the respective buckle component.